1. Field of the Invention
An embodiment of the present invention relates to a method for detecting a connector disengagement of an optical fiber amplifier having a rare earth doped optical fiber and a pumping light source, and a transmission optical fiber having at least one connector connecting portion connected to an output of the optical fiber amplifier, and relates to an optical fiber amplifier, and to a unit of an optical fiber amplifier and a transmission optical fiber connected thereto in which safety against disengagement of a connector is improved.
Priority is claimed to Japanese Patent Application No. 2004-71118, filed Mar. 12, 2004, the content of which is incorporated herein by reference.
2. Description of Related Art
Conventionally, an optical fiber amplifier, having a doped optical fiber that is doped with a rare-earth element, such as erbium, and a pumping light source, and a transmission optical fiber, having at least one connector connecting portion connected to an output of the optical fiber amplifier, forming a unit, has been proposed. In such a unit, an optical signal amplified in the optical fiber amplifier is transmitted via the transmission optical fiber.
In operation, high-power optical signal is continuously output from the optical fiber amplifier. The output-side connector of the optical fiber amplifier may accidentally be disengaged during maintenance activity, which may cause serious damage if the light emitted from the optical fiber is directly incident on an eye or the skin of a technician.
In a conventional technique, in order to prevent such an accident, an optical fiber amplifier was proposed in which connector disengagement of an output-side connector of a transmission optical fiber connected the optical fiber amplifier can be detected by monitoring reflected light of the optical signal from the disengaged connector, and output power is automatically halted or reduced upon detection of the connector disengagement (see Japanese Patent Nos. 2546499 and 2696064, and Japanese Unexamined Patent Application, First Publication No. H08-330649, for example).
Furthermore, in an optical transmission system, an optical fiber that is used to couple between an optical module, optical unit, or optical transmission unit may be broken, or a connector of an optical fiber amplifier may be disengaged, both of which may cause harm to technicians. Therefore, safety measures to prevent such accidents have been mandated (see Japanese Unexamined Patent Application, First Publication No. H11-121849, for example).
In addition, in recent years, an optical transmission unit and an optical transmission module have been proposed in which a connector disengagement or breakage of optical fiber can be detected by employing a simple circuit and conventional optical components without reducing optical signal output level (see Japanese Unexamined Patent Application, First Publication No. 2003-163642, for example).
In a conventional technique, a disengagement of an output-side connector in an optical fiber amplifier and a transmission optical fiber forming a unit is detected by measuring Fresnel reflection light from the output-side connector, and in this technique, it is assumed that the output-side connector is a non-angled end face connector, and an abutting end face is formed on a surface perpendicular to the longitudinal direction of the optical fiber, and connector disengagement is detected when the amount of reflected light is increased.
However, with this conventional technique, when an output-side angled end face connector in which an abutting end face is formed on a surface which is angled with respect to the longitudinal direction of the optical fiber is used as an output-side connector, the amount of reflected light from the disengaged connector becomes smaller compared to the amount of reflected light when the connector is engaged. Thus, connector disengagement cannot be detected.